Striking a balance between security, privacy and usability has become an important part of designing computing devices. For example, the ever-increasing functionality of mobile computing devices such as smartphones has made such devices more likely to be shared among several users. A common scenario occurs when a user is with a group of family members or friends, and someone in the group borrows the user's device to watch a video, look at images, listen to music, play a game, make a phone call, send a message, search for information on the Internet, etc. On the other hand, the high-level of functionality of mobile computing devices (and the high level of reliance and trust that many users have in their devices) also makes such devices more likely to contain sensitive information and pose a security risk if they are misused. Many users want to be able to share their devices without compromising their security or privacy.
Although there have been a variety of advances in balancing the security, privacy and usability of computing devices, there remains room for improvement.